1. Field of the Invention
The present invention relates to a device for reducing the temperature in the cylinder head of a multiple cylinder marine engine.
2. Description of Related Art
Personal watercrafts have become popular in recent years. This type of watercraft is quite sporting in nature and is designed to carry a rider and possibly one or two passengers. A relatively small hull of the personal watercraft commonly defines a rider's area above an engine compartment.
An internal combustion engine frequently powers a jet propulsion unit which propels the watercraft. The engine lies within the engine compartment in front of a tunnel formed on the underside of the watercraft hull. The jet propulsion unit is located within the tunnel and is driven by a drive shaft. The drive shaft commonly extends between the engine and the jet propulsion device, through a wall of the hull that forms a front gullet portion of the tunnel.
Personal watercrafts often employ an in-line, multi-cylinder, crankcase compression, two-cycle engine, usually including two or three cylinders. The engine conventionally lies within the engine compartment with the in-line cylinders aligned along a longitudinal axis of the watercraft's hull (in the bow-stern direction).
An exhaust manifold typically couples the exhaust ports of the engine cylinders to an exhaust system. The exhaust system discharges exhaust byproducts from the watercraft. The exhaust system commonly includes a water jacket which cools at least a portion of the exhaust system. At least a portion of the cooling water usually is introduced into the exhaust stream after an expansion chamber of the exhaust system to further silence exhaust noise and for discharge from the watercraft.
The engine usually includes a cylinder head which is mounted on top of a cylinder block and defines in part the combustion chamber of the engine. Water jackets are normally formed within the cylinder head and cylinder block to cool the engine heated by the combustion. Conventionally, the cylinder head has been manufactured by casting, thus necessitating complicated manufacturing processes to cast the passages that make up the water jacket within the cylinder head. Such complicated manufacturing processes result in increased manufacturing costs.